Aminoacidopathies Flashcards
Class of inherited errors of metabolism
There is an enzyme defect that inhibit the bodus’s ability to metabolize certain amino acids
Aminoacidopathies
Dife the concept of inborn errors of metabolism
1909 Garrod
Probable reasons of aminoacidopathies
A. Activity of a specific enzyme in the metabolic pathway
B. membrane transport system for amino acids
Aminoacidopathies
- Phenylketonuria
- Tyrosinemia
- Maple syrup Urine disease MSUD
- Alkaptonuria Black urine disease
- Cystinuria
Phenylalanine hydroxylase (PAH) dificiency
Phenylketonuria (PKU)
Catalyzes the conversion of phenylalanine to tyrosine
Phenylalanine hydroxylase
Deficiency in the enzymes for regeneration and synthesis of tetrabydrobiopterin (BH4)
Elevated blood levels of phenylalanine and deficient production of neurotransmitters from tyrosine and tryptophan
Hyperphenylalaninemia
Cofactor of enzymatic hydroxylation of the aromatic amino acids (phenylalanine, tyrosine, and tryptophan)
BH4
Phenylalanine levels
Greater than 1,200 micromol/L
New bor.: Upper limit of normal
120micromol/L (2mg/dl)
Metabolites of PKU
Blood and urine (musty odor)
When PKU is untreated
Very low IQ (below50)
Happy hormone
Serotonin
Synthesis of serotonin
Tryptophan
Defect in myelin formation
Insufficient synthesis of serotonin from tryptophan
Pigment synthesized from tyrosinase accumulation of phenylalanine competitively inhibits tyronase and impairs melanin formation
melanin
Essential precursor of tyrosine
Phenylalanine
How to reduce phenylalanine levels
Increasing the activity of the PAH enzyme
Follow phenylalanin-restricted diet
Characterized by the excretion of tyrosine and tyrosine catabolites in urine
Tyrosinemia
Most severe form of tyrosinemia
Low levels of the enzyme fumaryl acetoacetate hydrolase (5th enzyme)
Type 1 tyrosinemia
Leads to liver and kidney failure, problems affecting the nervous system, and and increase risk of cirrhosis or liver cancer
Type 1 Tyrosinemia
Manangement for type 1 Tyrosinemia
- Nitisone (NTBC)
BN: Orfadin, Nitryr
Class: Tyrosine Decredation Inhibitor - Low- phenylalanine and tyrosine Diet
Aka Richner-Hanhart syndrome
deficiency of tyrosine aminotransferase
Type 2 Tyrosinemia
S/Sx of type 2 Tyrosinemia
Mentally retarded
Excessive tearing, photophobia, eye pain, redness, and painful skin lesions on the palms and soles of the feet
Manangement of Type 2 Tyrosinemia
- No cure
- Diet of tyrosine, phenylalanine, and methionine
- Keratolytic and emollient for hyperkeratotic skin lesions
- Oral retinoids for persistent keratoderma
Rare disorder
Deficient of the enzyme 4-hydroxyphenylpyruvate dioxygenase
Type 3 Tyrosinemia
1st FDA approved enzyme substitution therapy as of 2018
Reduce blood Phe levels
Pegvalaise-PQPZ (Palynziq)
Magic sugar
Aspartame
Management of Type 3 Tyrosinemia
Phenylalanine and tyrosine-restricted diet
No treatment
Defective enzyme is homogentisate oxidase in tyrosine metabolism
Alkaptonuria
Urine in alkaptonuric patient resembles _____
Coke in color
Alkapton deposition in connective tissue, bones and various organs
Ochronosis
Deposition of pigment alkapton (in joints), produced from homogentisate
Arthritis
Management of Alkaptonuria
Medical therapy: ameliorate rate of pigment deposition
Ascorbic acid: retard the process of conversion of homogentisate to polymeric material
Nitisinone: reduce homogentisic acid excretion
Reduced activity of the enzyme branched-chain Ω ketoacid dehydrogenase
Blosk the normal metaboyof leucine, isoleucine, and valine
Maple Syrup Urine Disease (MSUD)
Degredation of propionyl CoA
Valine
Degredation of propionyl CoA and acetyl CoA
Isoleucine
Degredation of acetoacetate and acetyl CoA
Leucine
Urine odor of a defective alpha-keto acid dehydrogenase
Maple syrup or burnt sugar
Ω keto-analogues accumulate in a defective Ω-keto acid dehydrogenase
Ω-ketoisovalerate for valine
Ω-keto-§-methylvalerate for isoleucine
Ω-ketoisocaproate for leucine (transamination)
Characteristics maple syrup or burnt sugar odor
Urine, breath, and skin
Essential coenzyme in carbohydrate and amino acid metabolism
Thiamine
Management of MSUD
Consultation with neonatal/ paediatric nutritionist
Dietary restriction of branched-chain AA
Amino acid transport disorder
Defective transport of cystine and basic amino acid across renal tubule and the small intestine
Cystinuria
Involving the gene that codes for cystine transporter known as SLC3A1
Autosomal-recessive defect
Increased concentrations of cystine and basic amino acids. (ornithine, lysine, and arginine)
Urine amino acids
Normal in cystinuria
Plasma amino acid
Clinical presentation of cystinuria
- Cystine stones
- Chronic urinary tract infection
- Hematuria and dysuria
Decrease urinary cystine concentration
Hyperdiuresis
Patients should drink every hour
240 ml
Patient should drink before bedtime or atleast during the night
480 ml
Prevent the precipitation of cystine calculi and even aid in dissolution
Alkaline urine
Maintain urinary pH must be maintained at
7-7.5
Urinary alkalinizers
Potassium Citrate
Acetazolamide
Chelating agents which is a manage ment of Cystinuria
Penicillamine
Alpha-mercaltopropionylglycine
Bucillamine
Ability to dissociate the cystine molecule into disulphide moieties with muchh higher solubilities than parent molecule
Cystine-binding and Cystine-reducing agents
L-cystine dimethyl esters (L-CDME) and L-cystine methyl esters (L-CME)
Crystal Growth Inhibitors
First drug to help manange PKU
Sapropterin dihydrochloride (Kuvan)